Recent research has established the involvement of the thymus in the functioning of the immune system in mammalian species. It is in the thymus that haemopoietic stem cells become differentiated to mature immunocompetent lymphocytes called T-cells, which circulate to the blood, lymph, spleen and lymph nodes. The T-cells have immunological specificity and are involved in the cell-mediated immune responses, such as graft responses, response to viral infections, response to neoplasms and so forth. The body's response to antigenic material, such as for example in response to bacterial attack, is the province of antibody secreting cells, called B-cells, which are derived from bone marrow stem cells, but which are not differentiated in the thymus. The antibody response to an antigen, in many cases, requires the presence of appropriate T-cells, so that T-cells, and consequently the thymus, are necessary for the body's immune system to make not only cellular immunity responses, but also humoral antibody response. The thymic induction of the necessary differentiation of stem cells to T-cells is mediated by secretions of thymic hormones by the epithelial cells of the thymus.
The great interest in thymic substances, which may be implicated in various aspects of the immune response, has been instrumental in creating a very productive research effort. As a result of this research, a number of thymic substances have been reported in the literature. In the article by Goldstein and Maganaro in Annals of the New York Academy of Sciences, Volume 183, pps. 230-240, 1971, there are disclosures regarding the presence of a thymic polypeptide which causes a myasthenic neuromuscular block in animals, which is analogous to the human disease of myasthenia gravis. Further, in this article it was discovered that two distinct effects were caused by separate polypeptides in bovine thymus. One of these polypeptides, named "thymotoxin", was believed to cause myositis but it was further indicated that this polypeptide had not been isolated although it appeared to be a polypeptide of approximately 7,000 molecular weight, had a strong net positive charge and was retained on CM-Sephadex at a pH of 8.0.
In the publication "Nature", 247, 11, Jan. 4, 1975, there are described products identified as Thymin I and Thymin II which were found to be new polypeptides isolated from bovine thymus which have particular uses in various therapeutic areas. Because of the use of similar names for other products isolated from the thymus in the prior art, these Thymin I and Thymin II products are now named as Thymopoietin I and Thymopoietin II. These products and processes are described in U.S. Pat. No. 4,077,949. In U.S. Pat. No. 4,002,602 there are disclosed long chain polypeptides described as Ubiquitous Immunopoietic Polypeptides (UBIP), which polypeptide is a 74-amino acid polypeptide characterized by its ability to induce in vitro, in nanogram concentrations, the differentiation of both T-cell and B-cell immunocytes from precursors present in bone marrow or spleen. Thus, the polypeptide is useful in therapeutic areas involving thymic or immunity deficiencies and the like.
In U.S. Pat. No. 4,002,740 there are disclosed synthesized tridecapeptide compositions which have the capability of inducing the differentiation of T-lymphocytes but not of complement receptor B-lymphocytes. This polypeptide thus exhibited many of the characteristics of the long chain polypeptides isolated and named as thymopoietin in above-mentioned U.S. Pat. No. 4,077,949.
In U.S. Pat. No. 4,190,646, there are disclosed pentapeptides having the basic amino acid sequence: EQU R-NH-Arg-Lys-Asp-Val-Tyr-COR.sup.1
wherein R and R.sup.1 are substituents which do not substantially affect the biological activity of the basic active sequence. In the publication "Science", 204, 1309 (1979), it is disclosed that this pentapeptide arginyl-lysyl-aspartyl-valyl-tyrosine corresponds to amino acid residues 32-36 in thymopoietin and that in vitro this pentapeptide induced the differentiation of murine prothymocytes to thymocytes and inhibited differentiative induction of cells of the B lineage, which is a combination of actions that is unique to the parent molecule thymopoietin. In vivo it displayed the further thymopoietin property of reducing the high numbers of autologous rosette-forming cells normally present in the spleens of athymic mice.
The present invention relates to novel polypeptides having the ability to induce differentiation of T-lymphocytes.